The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
RF plasma has been extensively used for semiconductor manufacturing in recent decades. Field data shows that arcing is a main cause of wafer defects and damage. Real-time arc detection is critical to maintain and improve the yield in IC manufacturing.
Arcing is a sudden release of energy between parts in a plasma chamber, which accompanies fast electromagnetic transients typically in the range of 1 to 100 microseconds. Arc detection equipment generally includes two parts: a Langmuir probe for picking up signals and a real-time signal-processing unit. Based on the probe coupling, the detection can be classified as invasive and non-invasive techniques.
Referring now to FIG. 1, one of several configurations is shown of a radio frequency (RF) plasma delivery system 10. RF plasma delivery system 10 includes a RF generator 12 that provides power to a plasma chamber 14. An impedance matching network 16 can be inserted in a feed line between the output of RF generator 12 and the input of plasma chamber 14. A Langmuir probe 18 can be inserted into plasma chamber 14. Langmuir probe 18 generates a signal based on the plasma in plasma chamber 14. A data acquisition instrument 20 receives and processes the signal to characterize the plasma.
Langmuir probe 18 is a typical probe for plasma diagnostics and is well developed for determination of plasma characteristics including densities, temperatures, and energies. Langmuir probe 18 is essentially an antenna that is inserted into the plasma sheath to obtain plasma information. Because Langmuir probe 18 is inserted inside the plasma chamber 14, Langmuir probe 18 is invasive to the chamber processes. While this method of assessing the plasma behavior is accurate and informative, the intrusiveness of Langmuir probe 18 inhibits its use in a production environment.
Non-invasive arc detection can be based on broadband radiation that occurs during the arcing. Techniques using optical detection and florescence spectroscopy are based on this principle. These methods generally need a variety of sensors and are thus more expensive than Langmuir probe 18.